Purifying zinc metal



Nov. 13, 1934. P. M. GINDER in AL I 1,930,430

PURIFYING ZINC METAL Filed Jan. 10, 1953 '2 Sheets-Sheet l INVENTORS PHIL/P M G/NDER GEURGE 7. MAHLEI? 6 HOWARD M- CYI? J ATTORNEYS Patented Nov. 13,1934

UNITED- STATES PATENT OFFICE Cyr, Palmer-ton, Pa., assignors to The New Jersey Zinc Company, New York, N. Y., a corporation of New Jersey Application January 10, 1933, Serial No. 650,982

6 Claims.

This invention relates to purifying zinc metal by distillation, and has for its object the provision of certain improvements in the removal from impure zinc metal of lead and/ or cadmium and/or 6 other contaminating metals of higher or lower boiling points-than zinc.

In the copending application for Letters Patent of the United States of Leon S. Holstein and Philip M. Ginder, Ser. No. 540,566, filed May 28,

1931, there is disclosed a method of removing lead from zinc metal by distillation and partial condensation of the resulting metallic vapor in a reflux column, and an improved apparatus particularly adapted for the practice of that method is described in the copending application of Philip M. Ginder, Serial No. 648,056, filed December 20, 1932. In the copending application for Letters Patent of the United States of Philip M. Ginder, Willis M. Peirce and Robert K. Waring, Ser. No.

so 629,63, filed July 2, 1932, there is described a method of removing cadmium from zinc metal by the action of a reflux rectifying column. Throughout this specification and the appended claims, we have used the term reflux column 2. 5 to define a column or tower in which ascending metallic vapor moves in contact with descending (refluxing) molten metal resulting from condensation of ascending vapor; a substantial amount of refluxing molten metal being permitted to flow out of the base of the column and metallic vapor reaching the top of the column being appropriately recovered. We have discovered that certain operating and other advantages result from conveying the refluxing molten metal into a bath of molten metal other than the source or" metallic vapor for the reflux column. Thus, we have found that e veying the refluxing molten metal so vapor advantages is poss. le

tinuous distillation periods.

The present invention, based on the for discovery, involves passing the metallic sulting from the distillation of impure zinc metal through a reflux column, and permitting the condensed metal refluxing back from the column to flow into a bath of molten metal other than the source of metallic vapor for the reflux column. so The impure zinc metal may be distilled in a progressive series of retorts, each of which is operatively connected to an individual reflux column, and the molten metal refluxing back from each column may be permitted to flow intothe retort next in the progressive series to the retort delivering metallic vapor to that column. These and other advantageous applications of the principles of the invention will be best understood from the following description taken in conjunc tion with the accompanying drawings in which:

Figs. 1, 2 and 3 are an end elevation (partly in section), a front elevation and a top plan, p v y, of an apparatus for carrying out the invention in a progressive series of distillation retorts, and

Figs. 4, 5 and 6 are an end elevation (partly in section), a front elevation and a top plan, respectively, of a continuous refluxing apparatus for the production of cadmium-free zinc in accordance with the invention.

The apparatus of Figs. 1, 2 and 3 comprises a plurality of distillation retorts and associated reflux columns so arranged in a progressive series that the zinc metal distilled in the retort connected to the flrst reflux column refluxes into a second retort connected to a second reflux column, and the metal refluxing in the second column is conducted to a third retort connected to a third reflux column. Thus, the apparatus comprises three distillation retorts 10, 11 and 12 mounted in a common heating chamber or laboratory 13 of a furnace structure 14. Each retort is provided at its back. with a charging well 15 for supplying metal thereto and for removing residues therefrom. Any lead that may liquate from the molten metal in the retorts may be ladled out of the charging wells 15. The three retorts are operatively connected through pipes l6, l7 and 18 with reflux columns 19, 20 and 21. The reflux columns may be constructed in accordance with any of the modifications, or equiv aients thereof, disclosed in the aforementioned copending applications. The zinc vapor purified from lead passes from the top of the reflux columns through pipes 22, 23 and 24: into condensers 25, 26 and 27. The molten metal reaxing from column 19 flows from the bottom of the column through a pipe 28 the retort ll, similarly the refluxing molten metal from column as flows through pipe 29 into retort 12. The molten metal refluxing from column 21 through pipe 39 may be returned to retort l? or may be separately collected.

In the operation of the apparatus of Figs. 1, 2 and 3, the vapor evolved from the impure zinc metal charged into retort 10 contains less lead than does this impure metal, and the refluxing molten metal from the reflux column 19 removes a large proportion of the lead content of this vapor, so that the vapor discharged from the top of the reflux column 19 and recovered in the condenser 25 is relatively low in lead. The molten metal refluxing from the reflux column 19 distills in the retort 11 with the production in the same way of relatively pure zinc metal in the condenser 26. Similarly, 'the refluxing molten metal from the reflux column 20 is distilled in the retort l2 and subjected to the purifying action of reflux column 21.

Where fresh zinc metal contaminated with 40 sively enriched in cadmium and the refluxed mollead is charged into retort 10 only, its lead content ls progressively distributed among the three retorts 10, 11 and 12, so that lead-rich residues need not be removed from these retorts so frequently as would be necessary if the retorts were independently operated. Zinc metal of lower lead content than, that charged into retort 10 may be charged into retorts 11 and 12 through the charging wells 15, in which case the reflux columns 20 and 21 purify the zinc vapor of the lead in the refluxed metal from the preceding column or columns as well as of the lead present in the zinc metal charged into retorts 11 and 12.

Various changes may be made in the apparatus illustrated in Figs. 1, 2 and 3. Thus, the retorts may be heated in separate combustion chambers, instead of in a common chamber. Any number of retorts may be included in the progressive series. The pipes 16, 17 and 18 may enter their respective reflux columns at different levels, whereby metallic vapor enters the reflux columns at different levels in different stages in the progressive series.

Figs. 4, 5 and 6 illustrate an apparatus for purifying zinc from cadmium in a reflux or rectifying column, in which the molten metal refluxing from one rectifying column is conveyed to .a second retort for further redistillation and'puriflcation. One or more pairs of retorts 31 and 32 ing zinc metal which comprises distilling two 105 are appropriately mounted in a common combustion chamber, retort 31 being placed above or at a higher level than retort 32. The upper retort is, introduced into the retort. The cadmiumbearing zinc is volatilized in the retort 31, and the resulting vapor passes through a connection 34 into the rectifying column 35 where it is purified of cadmium by rectification. Thus, the vapor ascending the column 35 becomes progresten metal descending the column becomes progressively freed of cadmium. Cadmium vapor,

from the base of the reflux column 35 is delivered by an elbow pipe 38 to the lower retort 32, where it is in part revolatilized, the vapor passing up through the .pipe 38 into the reflux column 35 in counter-current with the descending molten metal. Zinc purified from cadmium is tapped from the lower retort 32 through a tap hole 39 at the back thereof. This apparatus is particularly appropriate for practicing that aspect of the process ofthe aforementioned application, Serial No. 620,634, in which the temperature gradient in a rectifying column for removing cadmium from zinc is established and controlled by supplying extra heat to the base of the col umn, the lower retort 32 functioning as the base We claim:-

1. The method of purifying zinc metal which comprises distilling a plurality of baths of impure molten zinc metal in a series of separate retort passing the impure zinc vapor from each of said retorts through an individuaLreflux column where a substantial amount of said vapor is condensed to molten zinc, and permitting file condensed zinc refluxing back from each of said columns to flow into the retort in the series, following the retort delivering impure zinc vapor thereto.

2. The method of purifying zinc metal which comprises distilling two baths of molten zinc metal in separate retorts, passing the impure zinc vapor from said retorts through a common reflux column, and permitting the molten zinc refluxing back from said column to flow into only one of said retorts.

3. The method of purifying zinc metal which comprises distilling'zinc metal in a progressive series of retorts, passing the impure zinc vapor from each of-said retorts through an individual reflux column where a substantial amount of the vapor is condensed to molten zinc, permitting the molten .zinc refluxing back from each of said columns to flow into the retort next in said progressive series to the retort delivering impure zinc vapor to that column.

4. The method of purifying cadmium-containbaths of molten'zinc metal containing cadmium in separate retorts. passing the impure zinc vapor from said retorts through a common reflux column, appropriately recovering from the top of said column a cadmium rich product, permitting 113 the molten zinc refluxing back from said column to flow into, only one of said retorts, removing low-cadmium zinc metal from the latter retort, and charging the cadmium-containing zinc metal to be purified into the other retort.

5. The method of purifying zinc metal which comprises distilling a bath of impure molten zinc metal in a retort, passing the resulting impure zinc vapor up through a reflux column in which the ascending vapor contacts with descending refluxing molten zinc resulting-from condensation of ascending vapor, permitting said descending refluxing molten zinc to flow into a bath of molten metal other than that in said retort and purifying the molten zinc reflux by distillation out 1 not reintroduced into the bath of impure zinc metal in the retort.

6. The method of purifying zinc metal which comprises distilling a bath of the impure molten zinc, passing the resulting impure zinc vapor through a reflux column where a substantial amount of the vapor is condensed to molten zinc,

permitting'the condensed molten zinc to descend 1. through said colunm in contact with the ascending impure zinc vapor, collecting the condensed zinc and distilling it out of contact with said bath of impure molten zinc so that the condensed molten zinc is purified and the impurities in said com densed molten zinc are not reintroduced into said I bath of impure molten zinc. PHILIP M. GINDER. GEORGE T. MAHLER. HOWARD M. CYR. 

